The leaders of Russia and the United States have agreed to slash their respective nuclear warhead arsenals by about 30 per cent, in a landmark pact that U.S. President Barack Obama said was a move in the right direction for both sides.

Under a pending agreement announced Friday, both countries will be limited to 1,550 long-range warheads, down from the 2,200 they are each currently permitted to hold. Each side will have seven years to reduce their nuclear inventory. They will also reduce the number of warheads and bombs they keep active on planes, ships and land.

The agreement requires verification actions by both parties, which U.S. Secretary of State Hillary Clinton said will "reduce the chance for misunderstanding and miscalculations."

Obama and Russian President Dmitry Medvedev are expected to sign off on the agreement in Prague on April 8, though the deal still needs to be ratified by lawmakers in their respective countries. It replaces a 1991 treaty that expired last December.

It was in Prague, nearly one year ago, that Obama called for the elimination of nuclear weapons and signalled his commitment to that goal.

In Washington, Obama said the agreement reached Friday with Moscow was part of his administration's ongoing efforts to "reset" the frosty relations Washington holds with the Russian government. He said the deal would also put both countries closer to undoing some of the damage that was done by the Cold War arms race.

"In many ways, nuclear weapons represent both the darkest days of the Cold War, and the most troubling threats of our time. Today, we have taken another step forward in leaving behind the legacy of the 20th century while building a more secure future for our children," Obama said Friday.

Natalya Timakova, a spokesperson for the Russian president, told the Interfax news agency that the treaty "reflects the balance of interests of both nations."

The White House released a statement that credited "American and Russian leadership" for improving the security of both nations and making nuclear security and global nonproliferation a continued priority.

After Obama spoke to reporters, Clinton said neither the U.S., nor Russia, needed such large stockpiles for defense purposes. Yet the two superpowers hold about 90 per cent of the world's nuclear weapons.

Adm. Mike Mullen, the U.S. Chairman of the Joint Chiefs of Staff, said the military supported the reductions called for in the agreement.

The military brass "stand solidly behind the treaty," he said.

CTV's Washington Bureau Chief, Paul Workman, said Obama has fought hard to forge a better working relationship with Moscow, but has been largely rebuffed in his efforts so far.

"The Russians did not extend very positively to his (Obama's) outstretched hand," Workman told Â鶹´«Ã½ Channel from Washington on Friday morning.

"So, they really have been working on this issue a lot, all on trying to get relations with the Russians back on track as much as they possibly can."

The United States and Russia now face common problems, with the threats posed by terrorism and rogue states being of particular concern to both countries, Workman said.

"It's not so much now that the United States and Russia are enemies in a Cold War -- nuclear power, nuclear warheads are not so much the issue for them," he said.

With files from The Associated Press